The preparation of aromatic and aliphatic-aromatic carbonic acid esters (carbonates) by transesterification starting from aliphatic carbonic acid esters and aromatic hydroxy compounds is known in principle. For example, a non-phosgene route to synthesize the diaryl carbonate of diphenyl carbonate (DPC) can be achieved through the transesterification of dimethyl carbonate (DMC) and phenol to produce phenyl methyl carbonate (PMC) as shown in Reaction (1), wherein the equilibrium constant at the range of operating temperatures can be on the order of 10−3,
followed by the subsequent disproportionation of PMC to produce diphenyl carbonate (DPC) as shown in Reaction (2),
wherein the additional formation of small amounts of an alkyl aryl ether (anisole) as the main reaction byproduct.
The production of diaryl carbonate in this manner is a highly energy intensive process due to the large amount of thermal energy needed in the first step, preparing the alkyl aryl carbonate. This energy is obtained from, for example, an external heating medium such as high-pressure steam. This large amount of thermal energy is used to overcome the unfavorable thermodynamics of the reaction scheme above. Without the introduction of this thermal energy, the reaction conversions are low. In addition to the large amount of thermal energy, a large excess amount of one of the reactants can be used to displace the equilibrium and to strip the more volatile alkyl alcohol (methanol) produced in Reaction (1). When such an excess of one of the reactants is used, the production process can require an extra recovery and recycle step.
A more efficient process of producing diaryl carbonate that could accomplish one or both of reducing the amount of thermal energy needed to facilitate the production of diaryl carbonate and reducing the amount of unreacted components and/or intermediate unreacted components that need to be recovered and recycled is desirable. Increasing the efficiency of the process could result in an increase its economic feasibility and/or reduce flue gas emissions directly associated with the energetic consumption.